Prior to the present invention trunk types of cartons provided with flip tops were devised and used in various forms for various purposes, and particularly for the packaging and distribution of highly viscous or stiffly frozen comestibles, such as ice cream. Softening of the carton chamber contents due to rises in temperature or initial deposition therein in the usual thick paste condition created problems of leakage which in turn led to the designing and embodiment of relatively complex features for reducing such leakage tendencies while attempting to avoid undue interference with ready carton opening and access to the contents by the customers. Attempts to overcome other related problems resorted to similar means. For example, the prior art patents of Barnes U.S. Pat. No. 3,315,870 of Apr. 25, 1967; Buttery U.S. Pat. No. 3,361,328 of Jan. 2, 1968; and Hoiles U.S. Pat. No. 3,833,165 of Sept. 3, 1974 are typical.
Barnes U.S. Pat. No. 3,315,870 proposes in such a flip-top carton the provision on certain of the four flaps stacked together to form an end closure provision of closely spaced and parallel short embossments to effect spacings for assuring leveling of lapped flaps so as to assure extended flat surface contact and adhesive coating carried thereby of an overlaid flap and contended resulting liquid tightness of the end closures.
Buttery U.S. Pat. No. 3,361,328 proposes similar provision of groups of adjacent short embossments and debossments in the end flaps that are hinged to the front and back panels to serve purposes similar to those of Barnes whereby leaking is alleged to be prevented.
Hoiles U.S. Pat. No. 3,833,165 proposes the provisions of a pair of short embossments on the inner face of each of the turned up end flaps which are hinged to the ends of the bottom panel that are to be lapped as the fourth flaps on the outsides of the end closure stacks. The marginal side zones of the inner face of each of these fourth flaps are provided with wide ribbons of adhesive to terminate short distances away from the hinge line of this flap to provide there potential leakage spaces, and the short embossments are provided in the latter to extend from the end of each adhesive ribbon to the hinge line to serve as a leakage block or dam.
An object of the present invention is to make efficient use of different embodiments of lines of embossments on the particular infolded flaps hinged to the ends of the flip-top panel which are inserted into the end stack closures to facilitate easy swing up and out thereof with the opening swing up of the top panel for easy access to the contents, and incidentally to serve as effective blockage means for reducing leakage.
The present invention is embodied in a trunk type of flip-top carton formed from a patterned one piece foldable blank of coated paperboard, or the like. This carton blank has a flip-top panel connected along a lateral fold line to a back panel which is, in turn, connected by a similar fold line to a bottom panel that is also connected by another lateral fold line to a front panel. The end edges of the flip-top panel and the two ends of each of the back, bottom and front panels are provided with end flaps hinged thereto by fold lines and are hingedly stackable at each end to form a container havng closed ends. The bottom panel has each of its end flaps swung upwardly as the first end flap in each end stack with its outermost face being a substantially smooth surface, and with the folded end flaps of the back and front panels in each end stack lapped in against each other over the outer face of this upfolded first end flap as the third and fourth end flaps in each stack, and with the latter end flaps anchored together. For the purpose of facilitating swinging down of the flip-top panel to closure of the top of the carton chamber with its end flaps swung inward to general alignment with the bottom panel end flaps as the second end flap in each end stack and slidably inserted by swing between the first end flap and the third and fourth anchored end flaps of each end stack, each of the flip-top panel second end flaps has its free edge opposite its hinged fold line so dimensioned and shaped as to permit such swinging insertion freely. Each of these second end flaps also has its inner side face which is opposed to the substantially smooth side face of the first end flap in each end stack provided with a plurality of lines of embossments spaced appreciably transversely from each other and extending obliquely in generally parallel relation thereacross from the general vicinity of the hinge fold line connection of this second flap toward the adjacent end of the flip-top panel. As a result, the swing out of each end stack of each of these second end flaps will be in the nature of generally longitudinal glide of each oblique embossment along the opposed substantially smooth surface of the first end flap.
Each of these oblique lines of embossment preferably is continuous but, if desired a plurality of relatively short breaks may be provided in each, so that the composite embossed sections together constitute a line of embossment. Each embossment preferably is arched transversely toward the opposed, substantially smooth, outer side face of the first end flap in each end stack for generally line contact therewith. This latter feature assures a minimum of frictional contact between the first and second end flaps so that swing out of the latter relative to the first is facilitated.
It is another object of the present invention further to reduce the degree of frictional contact between the first and second end flaps, particularly during swing of the latter relative to the first, by arranging the oblique lines of embossment along arcs of coaxial circles having their axes commonly located at the fold hinge line of the flip-top panel.
It is to be understood that if any such line of embossment be made up of a plurality of substantially straight line sectors they may be arranged as successive chords of each such circular arc. The anchorage of the third and fourth end flaps in each end stack may advantageously be of a nature as to avoid any necessity for use of adhesive in effecting such anchorage, which may be in the form of complementary parts that are readily engageable together and separable. For example, one of the third and fourth end flaps may have a transverse slot therein and the free end of the other may be shaped as a hook to engage in such slot.
It is a further object of the invention to realize these and other related advantages in economical and reliable manners.